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The Power of Food - Lecture in Review

Thursday 7 April 2016 4:37pm

The power of food starts, as you would expect, in the kitchen. We are introduced to mayonnaise in a whole new light, when visiting Professor Massimiano Bucchi asks us: What makes mayonnaise bind together?

Questions like these, Professor Bucchi explains, are common in the scientific exploration of food. The question demonstrates that many cooks are not scientist. Instead they are alchemists, they do not know the reasons behind the chemical reactions they cause on a daily basis. Why? Because understanding the ‘how’ of a recipe isn’t important until it suddenly doesn’t work.

He plays us a clip from the Italian show ‘Science in the Kitchen’. The presenter asks people on the street that same question: “What makes mayonnaise bind together?” And most respond as you would expect, with total confusion. What does he mean? Nothing makes it bind, it just binds. This is what Professor Bucchi means when he calls cooks alchemists. There is a treatment of food like it is unknowable, or magical, when really it is a series of straight forward chemical or physical reactions.

“Mayonnaise,” Professor Bucchi tells us, “is the combination of water, oil, and egg. People will tell you that the water has to be warm, or cold, they have superstitions about what makes it work and what makes it fail. The really important part is the egg. In the egg is a protein called lecithin which breaks the oil up into small bubbles and binds those little bubbles to the water. This is why the two don’t split, and this is why mayonnaise binds.”

He feels that cooking has been left behind as science has progressed, which he sees as a terrible shame. “The creation of a new recipe will have more impact on the lives of people than the discovery of a new solar system,” he says. He isn’t wrong, culture is built on the back of food. There are few things which feel more intimate or more sacred than a favourite dish, and maybe that is why science has had such trouble cracking in to cookery; because the importance of food isn’t in the ‘how’ or the ‘why’ it is in the way it makes us feel.

But why do we feel so strongly about food? Professor Dave Grattan stood up to take on this question. His answer: our brains are wired for it.

Most people in the western world can go to a supermarket and find almost anything they could want to eat, but 50,000 years ago food was much more scarce. With only limited capacity in our stomachs the brain learned to prioritise high calorie foods in order to make the most of any eating opportunity. There was no point in filling up on low calorie greens when honey or fruit was available. As a result the brain developed two different reward pathways for food: one for the taste, and another for the caloric content. But if our brain makes us feel good for eating, why aren’t we craving food all the time, why is it different to a drug addiction?

Both of the reward centres activated by food are mediated by how much our body needs food when we eat it. If we’re really hungry when we eat there is a much greater reward than if we eat when we’re not hungry. This is different to drugs, such as cocaine, which activate the reward centres of the brain to a consistently high amount every time they’re used.

This feedback system is linked in to several other hormonal systems in your body, systems which Professor Grattan researches at the University of Otago. The hormone leptin is produced by fat and signals to your brain when you have had enough food. If your body doesn’t produce leptin, or your leptin levels drop because you have lost weight, the brain believes that you are starving and will make food more rewarding. The hormone ghrelin is produced when the stomach is empty, this makes you feel hungry and incentivises eating. There is some evidence of ghrelin dysfunction in eating disorders such as anorexia.

It is by the combination of these hormones and reward pathways that the brain is able to so perfectly maintain body weight. You might disagree with that statement, in fact the audience was fairly disbelieving of the comment at first but consider this: an average human will eat more than 1 million calories per year. To maintain body weight the brain has to perfectly match energy input to energy output. To gain a single kilogram over the course of a year the brain has to be off by 6000 calories, which still makes the brain 99.4% correct. Your brain balances everything, from an extra spoonful of sugar in your coffee to the shortcut you took on your walk to work.

It is always running the numbers.

Your brain is biased to keeping your weight up, it doesn’t understand that food is plentiful and exercise sparse. It is waiting for a new famine, it is trying to keep your energy high just in case, it will always drive you to eat. It is this drive which has made food so consistently important in cultures across the world. So while we may not always understand our food, it is nice to know that our brains are paying attention and are always ready to reward us for having another bite.


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